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PubMedDate not supplied

The role of oxidative stress in nickel and chromate genotoxicity.

Some general principles regarding oxidative stress and molecular responses to toxic metals are presented in this manuscript. The remainder of the manuscript, however, will focus on the role of oxidative stress in particulate nickel-induced genetic damage and mutations. The phagocytosis of particulate nickel compounds and the dissolution of the particles inside the cell and the resulting oxidative stress produced in the nucleus is a key component of the nickel carcinogenic mechanism. The crosslinking of amino acids to DNA by nickel that does not involve direct participation of nickel in a ternary complex but nickel-induced oxidative stress will be discussed as well. The selective ability of particulate nickel compounds to silence the expression of genes located near heterochromatin and the effect of vitamin E on the genotoxicity and mutations induced by particulate and soluble nickel compounds will also be discussed. Particulate nickel compounds have been shown to produce more oxidative stress than water-soluble nickel compounds. In addition to nickel, the role of oxidative stress in chromate-induced genotoxicity will also be discussed with particular attention directed to the effects of vitamin E on mutations and chromosomal aberrations inducedby chromate.

Animals↗

PubMed1992

[Chronic chromate intoxication with renal tubular damage--report of a case].

A 46-year-old male chromium plating worker visited our hospital due to rhinorrhea, sneezing and cough with blood-tinged sputum for more than 10 years. He also had skin ulceration and chronic dermatitis on both hands Medical therapy was inefficient. Physical examinations revealed nasal septum perforation, severe inflammation of the nasopharynx cavity, and eczema of both hands. Laboratory investigations showed significant tubule proteinuria, enzymuria, hypercalciuria, etc. It is evident that renal tube damage was present in this patient. The blood chromium level was 25 ng/mL, and the 24-hour urine chromium excretion level was 2.8 mg/day. A pulmonary function test showed reduced functional residual capacity (FRC), which may be due to either long-term smoking or chromate acid exposure. To our knowledge this is the first case of renal tubal damage induced by chronic chromate intoxication Taiwan. Further evaluation of the occupational safety and health of chromium plating workers is needed on this island.

Chromates↗

PubMed1979

[The persistence of chromate allergy in cement eczema].

93 patients with contact allergy to chromates were followed up for 15 years during which time they were examined clinically and patch tested quantitatively at regular intervals. Results demonstrate that contact allergy to chromates and cement eczema differ from other occupational dermatoses mainly because of their persistence after a change of exposure and occupation. Explanations for this observation are offered.

Adult↗

PubMed1989

[Study of Ag-NOR, SCE and micronucleus in peripheral blood lymphocyte of chromate producers].

Ag-NOR, SCE and micronucleus test of peripheral blood lymphocyte obtained from 31 chromate producers had been studied. We found that (1) in the workers who had been exposed over eight years, the frequency of Ag-NOR, Ag-AA and SCE were 6.905 +/- 1.100, 0.380 +/- 0.652 and 8.190 +/- 3.727, but in the control group, 6.512 +/- 1.595, 0.215 +/- 0.529 and 7.171 +/- 2.683, respectively. So there was considerably significant difference between the exposed and the unexposed (P less than 0.01); (2) the frequency of micronuclei was 3.71 +/- 1.419% in the exposed group; however, in the control group it was 0.333 +/- 0.479%. So there was also remarkably significant difference between them (P less than 0.001). The observations lead the authors to conclude that the genetic material of the workers who have been working over eight years may be damaged because of being exposed to chromate.

Adult↗

PubMed1987

High hydrostatic pressure and chromate-induced effects on cell cycle kinetics.

Cell cycle kinetics was studied using the quenching of 33258 Hoechst fluorescence by bromodeoxyuridine incorporation to investigate effects of high pressure on the toxicity of a welding fume component--chromate. When exposing the glioma cells to 1 microM K2Cr2O7 at 1 bar, we observed a prolongation of DNA-synthesis phase, whereas cells exposed to 5 microM K2Cr2O7 did not pass through mitosis. Cells exposed to 1 or 5 microM chromate during the last part of DNA synthesis and during mitosis were not delayed in passing through mitosis. High pressure (100 bar) or pretreatment with pressure did not cause changes of cell cycle parameters. The combined exposure of 1 microM K2Cr2O7 and high pressure caused the same effect as observed for 1 microM K2Cr2O7 at 1 atm. However, an extra delay was observed in passing through mitosis for cells exposed to 100-bar pressure during the early part of their cell cycle.

Animals↗

PubMed1978

The use of chromium-51 sodium chromate for the detection of food and chemical sensitivities.

Both antibody mediated lysis of human RBC's and toxic hemolysis were found to occur with chemicals used as coloring agents for foods, drugs and cosmetics. Because of the strong chromaticity of these dyes, chromium-51 sodium chromate was bound to the hemoglobin of target human RBC's and its efflux was used as an indicator of lysis instead of spectrophotometry, which had been used with food antigens. The major antibody effect was noted when treatment of the target RBC's with antiIgG resulted in a marked inhibition of lysis, indicating that IgG is a lysis-promoting factor (LPF) in this system. Weaker effects were noted by treatment of the target RBC's with monospecific antisera for the other four classes of immunoglobulin and for alpha2-macroglobulin. No neutralizing effects were observed by pre-incubation of the dyes with autologous serum prior to the addition of RBC's.

Chromates↗

PubMed1983

Elemental changes at irritant reactions due to chromate and nickel in guinea-pig epidermis.

The present investigation was performed to examine the possibility of using energy dispersive X-ray microanalysis (EDX) to obtain information on epidermal reactions at irritant dermatitis. The elemental redistribution in the stratum germinativum and stratum spinosum of the guinea-pig epidermis after intradermal injection of a chromate and a nickel solution was studied in thick cryo-sections. The two solutions caused different changes in elemental content in both cell layers. Nickel sulfate caused a conspicuous decrease in K levels whereas Na and Cl were elevated in both cell layers. Potassium chromate caused an increase in Cl but lowered the P values. The result of this study show that it is possible to use EDX-analysis of thick skin sections to obtain information on physiologically relevant alterations in epidermis at irritant dermatitis.

Animals↗

PubMed1995

[Persistent reactive airway dysfunction syndrome after exposure to chromate].

A 42-year-old man was admitted to the hospital because of wheezing and dyspnea that began 20 minutes after accidental exposure to irritant gas containing chromate at a chrome pellet manufacturing plant. The patient had a positive skin reaction to chromite (Cr2O3). Reduction of FEV1.0 was observed 120 minutes after Cr2O3 inhalation challenge. By 150 minutes after Cr2O3 inhalation, FEV1.0 had decreased by 32%. Chest X-ray film revealed no abnormalities. Histological findings of the lung tissue obtained by open lung biopsy revealed bronchospasm and peri-bronchial inflammatory cell infiltration without bronchiolar obstruction, and thus bronchiolitis obliterans was ruled out. This patient fulfilled the criteria of reactive airway dysfunction syndrome (RADS) proposed by Brooks; onset of symptoms very soon after a single exposure to an irritant, persistence of asthmatic symptoms, obstructive pulmonary dysfunction, and the presence of airway hyperreactivity to methacholine. During the initial hospital stay, asthmatic symptoms were relieved by intensive anti-asthmatic treatment including oral and parenteral corticosteroids. However, the patient's asthmatic symptoms have lasted for eight years and necessitate the use of systemic steroids, and regular use of inhaled steroids and bronchodilators. We know of no previous reported case of RADS after chromate exposure.

Adult↗

PubMed2001

Effect of chromatic aberration on contrast sensitivity in pseudophakic eyes.

OBJECTIVE: To evaluate the effect of chromatic aberrations in pseudophakic eyes with various types of intraocular lenses (IOLs). PATIENTS AND METHODS: The study included 51 eyes of 33 patients who underwent cataract surgery. The eyes were divided into 3 groups according to the material from which their IOL was made: group 1, polymethyl methacrylate; group 2, silicone; and group 3, an acrylate/methacrylate copolymer. Ten normal phakic control eyes (group 4) underwent the same examination. Best-corrected distance visual acuity and contrast sensitivity were measured under white light and monochromatic light with wavelengths of 470 nm, 549 nm, and 630 nm, with the best correction under white light. RESULTS: There were no significant differences in best-corrected visual acuity and contrast sensitivity under the 549-nm monochromatic light in any group. However, under both white multichromatic light and 470- and 630-nm monochromatic light, the mean contrast sensitivity in group 3 tended to be lower, sometimes significantly, than in the other IOL groups. CONCLUSIONS: Our results showed that longitudinal chromatic aberrations of some IOLs may degrade the quality of the retinal image. Attention must be paid to the detailed optical performance of IOL materials to achieve good visual function.

Acrylates↗

PubMed1998

Chromatic distortion during angioscopy: assessment and correction by quantitative colorimetric angioscopic analysis.

Angioscopy represents a diagnostic tool with the unique ability of assessing the true color of intravascular structures. Current angioscopic interpretation is entirely subjective, however, and the visual interpretation of color has been shown to be marginal at best. The quantitative colorimetric angioscopic analysis system permits the full characterization of angioscopic color using two parameters (C1 and C2), derived from a custom color coordinate system, that are independent of illuminating light intensity. Measurement variability was found to be low (coefficient of variation = 0.06-0.64%), and relatively stable colorimetric values were obtained even at the extremes of illumination power. Variability between different angioscopic catheters was good (maximum difference for C1, 0.022; for C2, 0.015). Catheter flexion did not significantly distort color transmission. Although the fiber optic illumination bundle was found to impart a slight yellow tint to objects in view (deltaC1 = 0.020, deltaC2 = 0.024, P < 0.0001) and the imaging bundle in isolation imparted a slight red tint (deltaC1 = 0.043, deltaC2 = -0.027, P < 0.0001), both of these artifacts could be corrected by proper white balancing. Finally, evaluation of regional chromatic characteristics revealed a radially symmetric and progressive blue shift in measured color when moving from the periphery to the center of an angioscopic image. An algorithm was developed that could automatically correct 93.0-94.3% of this error and provide accurate colorimetric measurements independent of spatial location within the angioscopic field. In summary, quantitative colorimetric angioscopic analysis provides objective and highly reproducible measurements of angioscopic color. This technique can correct for important chromatic distortions present in modern angioscopic systems. It can also help overcome current limitations in angioscopy research and clinical use imposed by the reliance on visual perception of color.

Algorithms↗

PubMed2002

Chromate sensitivity in fission yeast is caused by increased glutathione reductase activity and peroxide overproduction.

The Cr(VI)-sensitive mutant chr-51S of the Schizosaccharomyces pombe accumulated chromate (CrO(4) (2-)) and reduced Cr(V) to much greater extent, than did its parental strain 6 chr(+). Sublethal doses of K(2)Cr(2)O(7) did not induce any adaptive stress response, while H(2)O(2) or menadione pretreatment proved protective against the cell injuries caused by Cr(VI). The intracellular GSH concentration in chr-51S cells was approximately half of that for the 6 chr(+). Moreover, the glutathione disulfide reducing capacity of chr-51S was characterized by significantly increased glutathione reductase (GR) and glucose-6-phosphate dehydrogenase activities. These data strongly suggested that, instead of GSH, the NADPH/GR system was the major one-electron Cr(VI) reductant in vivo. The increased Cr(V) reduction in chr-51S mutant was accompanied by high intracellular superoxide and peroxide concentrations, required for formation of the hydroxyl radical ((*)OH). The decreased intracellular GSH levels and the Cr(VI)-sensitive phenotype of the chr-51S cells indicates that GSH might act effectively against chromate by scavenging (*)OH.

Chromium↗

PubMed1993

Influence of o-phenanthroline on DNA single-strand breaks, alkali-labile sites, glutathione reductase, and formation of chromium(V) in Chinese hamster V-79 cells treated with sodium chromate (VI).

The effect of the cell-permeable metal chelator o-phenanthroline (OP) on the formation of chromium(V), DNA breaks, alkali-labile sites, and enzyme inhibition of chromium(VI) was studied using Chinese hamster V-79 cells. Alkaline elution assays demonstrated that treatment with OP (100-500 microM) resulted in a dose-dependent decrease in cellular levels of either alkali-labile sites or the combination of alkali-labile sites plus DNA single-strand breaks caused by Na2CrO4. Cellular treatment with OP also attenuated the inhibition of glutathione reductase attributed to Na2CrO4. Under the same experimental conditions, the cellular uptake of chromate was not affected by OP. ESR studies revealed that cellular treatment with OP (100-500 microM) resulted in a concentration-dependent decrease in the level of chromium(V) intermediate in cells treated with Na2CrO4. Furthermore, OP inhibited the chromium(V) complex that formed during the reaction of Na2CrO4 with glutathione in vitro, resulting in the decrease of chromium(V)-mediated hydroxyl radical formation while neither the reduction of chromium(VI) nor the formation of the chromium(VI)-glutathione complex was affected, indicating that OP may react with chromium(V) but not with chromium(VI). These results suggest that the metal chelator OP decreases chromate-induced alkali-labile sites or the combination of alkali-labile sites plus DNA strand breaks, as well as chromium inhibition of glutathione reductase, possibly through its ability to directly decrease chromium(V) complex in cells.

Animals↗

PubMed2002

Chromate content versus particle size for aircraft paints.

Many industries rely on the corrosion inhibiting properties of chromate-containing primer paints to protect metal from oxidation. However, chromate contains hexavalent chromium (Cr(6+)), a known human carcinogen. The concentration of Cr(6+) as a function of paint particle size has important implications to worker health and environmental release from paint facilities. This research examines Cr(6+) content as a function of particle size for three types of aircraft primer paints: solvent-based epoxy-polyamide, water-based epoxy-polyamide, and solvent-based polyurethane. Cascade impactors were used to collect and separate paint particles based on their aerodynamic diameter, from 0.7 to 34.1 microm. The mass of the dry paint collected at each stage was determined and an atomic absorption spectrometer was used to analyze for Cr(6+) content. For all three paints, particles less than 7.0 microm contained disproportionately less Cr(6+) per mass of dry paint than larger particles, and the Cr(6+)concentration decreased substantially as particle size decreased. The smallest particles, 0.7 to 1.0 microm, contained approximately 10% of the Cr(6+) content, per mass of dry paint, compared to particles larger than 7.0 microm. The paint gun settings of air to paint ratio was found to have no influence on the Cr(6+) bias.

Aircraft↗

PubMed2002

Chromate dissociation from three types of paint particles.

Chromate-containing primer paints are used to inhibit corrosion on metal surfaces. Though chromate contains hexavalent chromium (Cr(6+)), a human carcinogen, there is little epidemiological evidence of increased lung cancer among spray painters. One reason may be that the paint matrix hinders the release of Cr(6+) from the paint particle during the time that the particle is within the lungs. This study measures the mass of Cr(6+) released from particles originating from three types of paint particles: solvent-borne epoxy, water-borne epoxy, and polyurethane. Impingers were used to collect paint particles into water and particles were held in the water at rest for 1 and 24 h residence times. Particles were then separated from the water by centrifugation. The supernatant was tested for dissolved Cr(6+), which was compared to the total Cr(6+) (dissolved Cr(6+) plus Cr(6+) in particles). The mean fractions of Cr(6+) released into the water after 1 and 24 hours for each primer averaged: 70 and 85 (solvent epoxy), 74 and 84% (water epoxy), and 94 and 95% (polyurethane). Correlations between particle size and the fraction of Cr(6+) released indicate that smaller particles (<5 microm) release a larger fraction of Cr(6+) versus larger particles (>5 microm).

Carcinogens, Environmental↗

PubMed1994

Complementary chromatic adaptation: photoperception to gene regulation.

Many photosynthetic organisms can acclimate to the quantity and quality of light present in their environment. In certain cyanobacteria the wavelengths of light in the environment control the synthesis of specific polypeptides of the light harvesting antenna complex or phycobilisome. This phenomenon, called complementary chromatic adaptation, is most dramatically observed in a comparison of cyanobacteria after growth in green light and red light. In red light-grown cells the phycobilisome is largely composed of phycocyanin and its associated linker polypeptides (the latter are important for the assembly of the phycocyanin subunits and their placement within the light harvesting structure); the organisms appear blue-green in color. In green light-grown cells the phycobilisome is largely composed of phycoerythrin and its associated linker polypeptides; the organisms appear red in color. The ways in which these cyanobacteria sense their changing light environment and the regulatory elements involved in controlling the process of complementary chromatic adaptation are discussed in this review.

Adaptation, Physiological↗

PubMed1990

A method for removal of toxic chromium using dialysis-sac cultures of a chromate-reducing strain of Enterobacter cloacae.

A method for removal of toxic hexavalent chromium (chromate: CrO2-4) was developed by use of dialysis-sac cultures of a chromate-reducing strain of Enterobacter cloacae (HO1). E. cloacae strain HO1 cells were put in dialysis (semipermeable membrane) sacs, and the sacs were submerged in water containing toxic CrO2-4. The dialysis sacs allowed CrO2-4 to diffuse into the culture, and CrO2-4 was reduced anaerobically in the dialysis sacs by the E. cloacae cells. Because reduced chromium readily formed insoluble chromium hydroxides in the dialysis sacs, the greater part of reduced chromium was unable to diffuse out through the semipermeable membrane. Thus the dialysis culture of E. cloacae strain HO1 could successfully remove toxic chromium from the surrounding water. If the initial concentration of CrO2-4 was less than 4 mM (208 ppm as chromium), about 90% of the total chromium could be removed from water by the described method.

Bacteriological Techniques↗

PubMed1978

[Spectral sensitivity of off-response in human VECP during selective chromatic adaptation (author's transl)].

The spectral sensitivity of the visual system of man during selective chromatic adaptation was determined. The criterion was an off-response of constant amplitude in the evoked cortical potential. Criterion of height of response differed among the subjects investigated. Generally, a pupillary radiant intensity between 0.4 and 1.0 lg unit above the sensory threshold was used. With stimulation of both the green- and the red-sensitive mechanism, the sensitivity of the off-response was low. It was high if either the green or the red mechanism were suppressed by selective chromatic adaptation. Demonstration of an opponent color mechanism in the visual system was easier with recording of the off-response in the VECP than with determination of the sensory threshold. The presence of the blue-sensitive mechanism as revealed by the VECP off-response was shown for light stimuli near the sensory threshold during adaptation which orange and red light for a late response of low amplitude.

Adaptation, Physiological↗

PubMed2001

Pupillary response to chromatic flicker.

There is significant evidence for higher-level cortical control of pupillary responses to visual stimuli, suggesting that factors other than luminance changes may induce a pupillary response. In the present study, the pupillary responses to equiluminant flickering stimuli in a range of 3-13 Hz were examined. Flicker stimuli included color-black (luminance-modulated) and color-color (hue-modulated) flicker. Equiluminance was determined both by objective luminance measures as well as by subjective, perceptual equiluminance for each subject. For both objectively and subjectively equiluminant flicker, significant, sustained pupillary constrictions were recorded. The magnitude of these responses was sensitive to both color and frequency parameters; red-blue color-paired flicker consistently produced the strongest constrictions. These responses occurred even when the flicker was of a lower luminance, both physically and perceptually, than a preceding nonflickering color, indicating that chromatic rather than luminance-sensitive mechanisms are involved in this response. Interestingly, the color- and frequency-sensitivity of constriction parallels those of flickers which maximally stimulate photosensitive epileptic patients, raising the possibility that chromatic response may be a factor in photosensitivity.

Adolescent↗